Archaeometric Analysis of the Objects from the Scala Santa (Holy Stairs) in the Crypt under the Piarist Church in Cracow (Poland)

Conservators extracted and preserved reliquaries hidden in the steps of the right flight of the Holy Stairs erected in the Piarist church crypt in Cracow (Poland). Three items from among 59 reliquaries were selected for specialist analyses: a framed, transparent cross containing a particle of the True Cross, and two opaque beads; an ornamented blue one without a hole and a drilled black one were analysed using non-destructive and non-invasive methods. The methods included scanning electron microscopy coupled with energy dispersive X-ray spectrometry, Raman microspectroscopy and X-ray diffractometry. The reliquary cross was found to be made of rock crystal and framed with an alloy of gold, silver and probably copper. The beads are made of glass; the blue bead represents forest plant-ash potash–lime glass and the black one, plant-ash soda–lime glass. Cobalt, probably along with copper, was used to produce the colour of the blue bead; manganese and iron ions were used to produce that of the black bead. Lead was present in both beads as one of the minor components and also as a component of corrosion products on their surfaces and probably also as part of the filler for the ornamentation of the blue bead. Nevertheless, it cannot be ruled out that the lead compounds were introduced intentionally to emphasize the bead ornamentation. The possible place and date of manufacture of the artefacts were also discussed.